Timing belts and chains are used on overhead camshaft engines, because the camshaft is further from the crankshaft.
This is a typical chain drive system. It uses a hydraulic tensioner which is fed by oil under pressure from the lubrication system. The chain also uses guides to reduce noise and vibration.
The toothed timing belt is made of fibreglass or wire- reinforced synthetic rubber. Its teeth match those on the crankshaft and camshaft pulleys.
Timing belts are quieter than chains but usually require regular manual tensioning.
They also have a shorter life than chains. They need regular replacing around 50,000 to 60,000 miles or 80,000 to 100,000 kilometers.
If a belt breaks, it is not only inconvenient but on some engines it can cause a lot of damage